1. Field of the Invention
The present invention relates to an anterior segment photographing apparatus for producing images of sections of the anterior segment of an eye to be examined by projecting a slit light beam on the eye.
2. Description of the Related Art
A known anterior segment photographing apparatus for photographing the sections of the anterior segment of the eye to be examined produces images of sections of the anterior segment by illuminating the anterior segment including a cornea and a crystalline lens with a slit light beam, projecting the slit light beam from the front of the eye to be examined along the lens axis thereof, and receiving images of sections of the anterior segment thus illuminated from a direction oblique to the lens axis thereof.
The anterior segment photographing apparatus of this kind sections the anterior segment by planes including meridians around the lens axis of the eye to be examined, and photographs images of sections of the anterior segment. The anterior segment photographing apparatus in a related art is provided with a photographing optical system having an optical axis inclined at a predetermined angle to the lens axis of the eye to be examined in which the photographing optical system is turned around the lens axis of the eye.
Since the photographing optical system of this anterior segment photographing apparatus of the related art is disposed with its optical axis inclined at the predetermined angle to the lens axis of the eye to be examined, a space must be secured for the turning of the photographing optical system around the lens axis of the eye, besides a large rotative driving mechanism is necessary to let the photographing optical system revolve, and accordingly the anterior segment photographing apparatus is necessarily large.
Since the rotative driving mechanism is large, the photographing optical system can be revolved only at low revolving speeds, so that much time is necessary for obtaining an image of a section of the anterior segment in each plane including a meridian.
Accordingly, it is an object of the present invention to provide an anterior segment photographing apparatus having small construction and capable of obtaining an image of a section of the anterior segment in each plane including a meridian in a short time.
According to a first aspect of the present invention, an anterior segment photographing apparatus comprises a slit light beam projecting system for projecting a slit light beam on an eye to be examined, an image forming optical system disposed right in front of the eye capable of forming an image of a section of the anterior segment of the eye represented by the slit light beam reflected from the eye on a light receiving surface, a concave mirror having a concave reflecting surface in a shape of rotational symmetry with respect to the optical axis of the image forming optical system capable of collecting and reflecting the slit light beam reflected from the eye, and a reflecting mirror for reflecting the light reflected from the concave mirror toward the image forming optical system.
Accordingly, the anterior segment photographing apparatus can be formed small in construction and is capable of quickly producing an image of a section of the anterior segment in a plane including a meridian.
According to a second aspect of the present invention, in the anterior segment photographing apparatus, the slit light beam can be turned around the optical axis of the slit light beam projecting system, and the image forming optical system and the reflecting mirror are turned around the optical axis of the image forming optical system according to the turn of the slit light beam.
According to a third aspect of the present invention, in the anterior segment photographing apparatus, the reflecting mirror has a cylindrical reflecting surface.
According to a fourth aspect of the present invention, in the anterior segment photographing apparatus, the concave mirror forms an image of a section of the anterior segment of the eye to be examined on a first image surface, and the image forming optical system forms the image of the section of the anterior segment formed on the first image surface on the light receiving surface.